Research Reports

Allowable Axle Loads on Pavements

Principal Investigator:

This report documents the development of a procedure to determine the structural adequacy and need of seasonal
axle load restrictions for Minnesota low-volume roads. This procedure has been implemented into a new program,
TONN2010. Since it is anticipated that the results of this study will be widely used by Mn/DOT, city, and county
engineers, as well as consulting engineers involved in analysis of the falling weight deflectometer (FWD) data
collected by the transportation agencies, an emphasis was made on development of a simple, easy to implement
procedure. To simplify the procedure?s implementation, the number of inputs was minimized. TONN2010 utilizes
pavement layer thicknesses, FWD deflection basins, air temperature of the previous day, pavement surface
temperature at the time of testing, pavement location, and anticipated traffic. All the inputs required by
TONN2010 can be easily obtained by the user. Using these inputs, TONN2010 proceeds to 1) backcalculate layer
moduli using the backcalculation procedure developed in this study, 2) adjust the backcalculated moduli using
MnPAVE temperature and seasonal adjustment factors, and 3) estimate pavement axle load capacity by
mechanistic-empirical analysis. In addition to detailing TONN2010, the report further describes selection of the
damage models, development of the backcalculation design procedure, determination of the critical structural
responses, development of new structural rating indexes, and finally the calibration and validation of the proposed
procedure.